Using Windows Home Server the device attempts to configure itself and the router to allow access from the outside. By default, ports forwarding requests fail.
See http://www.linksysinfo.org/index.php?threads/upnp-on-but-whs-still-complains-about-port-forwarding.33553/ for a description of the issue, and the nvram settings needed to allow it.
Would it be possible to expose this within the Tomato web interface, and possibly to allow a finer control than the whole range?
(I finally today ipgraded to a more current version of TomatoUSB than I had been using for the last 2 years, and of course had to rediscover what was needed for WHS to work).